Now my question - WHO saw a Neanderthal change into a Homo sapien?
Neanderthal didn't evolve into homo sapiens.
There was some cross breeding (many humans have a % of neanderthal DNA), but homo sapiens didn't evolve from neanderthal.
At best, neanderthal were our cousins (on a species level).
As for your silly question.... Ignoring the error of your neanderthal comment... no, nobody has ever observed a process that takes millions of years to unfold.
Who has ever seen Pluto complete an orbit?
Nobody, that's who. You know why? First, because it takes multiple lifetimes. Second, because we haven't even known long enough about Pluto for it to complete an orbit since it's discovery.
Yet, we know
exactly how long it takes to complete an orbit.
So, who has seen medieval english develop into modern english?
Or Latin into spanish, french, portugese, italian,..?
Who witness the transformation or evolution?
Nobody.
But we can see confirmation of common ancestry in our collective DNA.
None? Then the evidence are just guesses and mere imaginations.
You don't seem to understand what evidence is. Evidence is about much more then mere "eyewitness testimony".
In fact, and quite ironically, "eyewitness testimony" is the least credible type of evidence you could possibly come up with.
Countless murder convicts were falsely put in prison based on "eyewitness testimony".
They later were set free when actual evidence came in, like DNA evidence.
A single piece of objective evidence, will instantly overrule 100 opinions or "testimonies" or "anecdotes".
In case of evolution, common ancestry of species in particular, that objective (verifiable, testable, demonstrable) evidence, is provided by the genetic record primarily.
But off course also the fossil record, comparative anatomy, biogeography, etc etc...
Maybe you should try to inform yourself on the unified field theory of biology and actually try to understand it, before insisting on arguing against it.